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Why "front mounted" vs. regular for speakers?

3/25/2004 6:34 PM
Joel	Why "front mounted" vs. regular for speakers? Hi all, Some speakers are mounted by cutting a hole in the baffle, putting the magnet end through the hole, and screwing/bolting the speaker onto the front side of the baffle. I believe this is called "front mounting"? Some speakers are mounted by cutting a hole in the baffle, and mounting the speaker on the inside of the cabinet - screwing/bolting the speaker to the back side of the baffle. What factors are there in making this choice? Are there general rules for why you would do it one way versus another? Thanks for any help, Joel

3/25/2004 6:34 PM

Joel

Why "front mounted" vs. regular for speakers?

Hi all,

Some speakers are mounted by cutting a hole in the baffle, putting the magnet end through the hole, and screwing/bolting the speaker onto the front side of the baffle. I believe this is called "front mounting"?

Some speakers are mounted by cutting a hole in the baffle, and mounting the speaker on the inside of the cabinet - screwing/bolting the speaker to the back side of the baffle.

What factors are there in making this choice? Are there general rules for why you would do it one way versus another?

Thanks for any help,
Joel

3/25/2004 8:22 PM
kg	rear mounting allows you to use the built-in gasket found on many speakers. it also ever-so-slightly "horn loads" the cone of the speaker. to remove the speaker you must disassemble or otherwise gain access to the rear of the baffle. it also protects the cone a bit more by virtue of the fact that it is recessed by the thickness of the baffle itself. hth ken

3/25/2004 10:36 PM
Rick S	I think the choice to use front mounted speakers is most often based on economy. You can save some cost if you don't need a removable back, and you will find many of the cheap cabs front loaded. Rick S

3/26/2004 12:35 AM
Joel	Makes sense, Rick. Thanks.

3/26/2004 12:34 AM
Joel	Thanks Ken! What does "horn load" mean? (and please - don't tell me its part of the porn industry lexicon).

3/26/2004 3:08 PM
kg	horn loading explained to expand on what enzo has said... the speaker cone to air interface is absolutely HORRIBLE when it comes to efficiency. the reason for this is a matter of matching impedances. you may know that in electronics, maximum power transfer comes when the source impedance is equal to the load impedance. [1] the same is true when it comes to acoustics. the speaker cone itself is a low impedance source. it has "balls" to it, so to speak. it is driven by a powerful motor, which can exert quite a bit of force. as an example, if you put your hand on the cone while a bass frequency is being reproduced, the cone will move your hand. you can literally feel it push on it. contrast that with the impedance of free air. it is quite easy to push your hand through the air. in fact, you really don't feel the resistance of the air AT ALL most of the time. so we have a massively mismatched junction of impedances here. and as a result, an abysmal efficiency rating. something like <<10% of the electrical energy put into a speaker is actually transduced into acoustic energy. in most cases it's probably less than 5%. what horn loading does is to increase the impedance of the air itself. by restricting the space into which the air may expand and contract, the degree to which the air "pushes back" on the speaker cone is increased greatly. the impedances of both the air and the cone are closer in value. as a result, the horn loaded speaker enjoys a far greater electrical->acoustic efficiency. horn loading does not necessarily mean a horn; you achieve the same effect when you place speakers at points in the room which limit the airspace into which they radiate. you know that you will enjoy greater output from the speaker if it is moved from floating in free air in the middle of the room (free space) to sitting on the floor in the middle of the room (half space). if you move it to the middle of the junction between floor and wall you will increase efficiency further (quarter space). finally, moving the speaker to the corner of the room, where it meets two walls and a floor will net you even greater efficiency (eighth space). horn loading is merely an extension of this concept of restricing the degree of compression and rarifaction of the air. the major benefit is increased effiency, which for a given amplifier electrical power output means greater acoustic output power. hth ken [1] to be perfectly accurate, max power transfer occurs when the loads are _conjugates_ of one another, which takes into account their reactances.

3/26/2004 3:08 PM

horn loading explained

to expand on what enzo has said...

the speaker cone to air interface is absolutely HORRIBLE when it comes to efficiency.

the reason for this is a matter of matching impedances. you may know that in electronics, maximum power transfer comes when the source impedance is equal to the load impedance. [1] the same is true when it comes to acoustics.

the speaker cone itself is a low impedance source. it has "balls" to it, so to speak. it is driven by a powerful motor, which can exert quite a bit of force. as an example, if you put your hand on the cone while a bass frequency is being reproduced, the cone will move your hand. you can literally feel it push on it.

contrast that with the impedance of free air. it is quite easy to push your hand through the air. in fact, you really don't feel the resistance of the air AT ALL most of the time.

so we have a massively mismatched junction of impedances here. and as a result, an abysmal efficiency rating. something like <<10% of the electrical energy put into a speaker is actually transduced into acoustic energy. in most cases it's probably less than 5%.

what horn loading does is to increase the impedance of the air itself. by restricting the space into which the air may expand and contract, the degree to which the air "pushes back" on the speaker cone is increased greatly. the impedances of both the air and the cone are closer in value. as a result, the horn loaded speaker enjoys a far greater electrical->acoustic efficiency.

horn loading does not necessarily mean a horn; you achieve the same effect when you place speakers at points in the room which limit the airspace into which they radiate. you know that you will enjoy greater output from the speaker if it is moved from floating in free air in the middle of the room (free space) to sitting on the floor in the middle of the room (half space). if you move it to the middle of the junction between floor and wall you will increase efficiency further (quarter space). finally, moving the speaker to the corner of the room, where it meets two walls and a floor will net you even greater efficiency (eighth space).

horn loading is merely an extension of this concept of restricing the degree of compression and rarifaction of the air. the major benefit is increased effiency, which for a given amplifier electrical power output means greater acoustic output power.

hth
ken

[1] to be perfectly accurate, max power transfer occurs when the loads are _conjugates_ of one another, which takes into account their reactances.

3/29/2004 9:23 PM
Shea	Kinda like a carb spacer? Just to make sure this discussion stays complicated, is the effect of horn loading similar to the effect of sticking a 1/2" spacer between your carb and manifold? (disregarding the thermal effect) Does the old Fender Tone Ring work on this principle? Does it have a noticable effect? Shea

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